Silver motor stator for implantable blood pump

ABSTRACT

In one embodiment of the present invention, an implantable blood pump includes a housing defining a flow path, a rotor positioned within the flow path, and a motor including a stator, positioned outside of said housing, the stator including a length of silver wire, wherein the silver wire is not positioned within a hermetically sealed compartment once the blood pump is ready for implantation into a patient in need thereof. The present invention may also include a method of implanting the implantable blood pump including the step of implanting the blood pump within the patient and within or adjacent to the vasculature.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of the filing data of U.S.Provisional Patent Application No. 61/646,028, filed May 11, 2012, thedisclosure of which is hereby incorporated herein by reference.

BACKGROUND OF THE INVENTION

Implantable blood pumps are typically used in the later stages of heartdisease or after trauma to the heart, when the heart itself is too weakor otherwise incapable of creating sufficient blood pressure and bloodcirculation to satisfy body function.

Various blood pumps are already in use for the purpose of augmenting orreplacing the blood pumping action of damaged or diseased hearts. Bloodpumps are commonly used in three situations: (1) for acute supportduring cardio-pulmonary operations; (2) for short-term support whileawaiting recovery of the heart from surgery; or (3) as a bridge to keepa patient alive while awaiting heart transplantation. The pumps may bedesigned to provide at least one of right or left ventricular assist,although left ventricular assist is the most common application in thatit is far more common for the left ventricle to become diseased ordamaged than it is for the right ventricle.

Implantable blood pumps comprise miniaturized pumps capable of beingpercutaneously or surgically introduced into or adjacent to the vascularsystem of a patient, typically to provide left or right heart support,or even total heart support. Various types of blood pumps include radialflow centrifugal pumps and axial flow pumps. Such pumps typically usemagnetic or electromagnetic forces, for example, to power a magneticrotor placed within or adjacent to a flow path of blood moving into orout of the heart. An at least one electromagnet, or stator, ispositioned around the outside of a tubular casing containing the flowpath, whereas the rotor is disposed inside the casing.

The rotor is magnetic. The stator typically is a set of electricallyconductive wire coils. The rotor is energized by a power source withalternating currents through the coils to create a rotating magneticfield. That is, the field is directed transverse to the axis of thetubular casing, and the direction of the field rotates about the axis ofthe casing. As the field rotates, the rotor spins about its axis thusadvancing the blood within the flow path. The power source may beimplanted somewhere within the body of the patient or may be external tothe patient, as is known in the art.

One such pump, disclosed in U.S. Pat. No. 7,575,423, the entirety ofwhich is incorporated by reference herein as if fully set forth herein,is a centrifugal-type pump. FIGS. 3 and 7 of U.S. Pat. No. 7,575,423have been reproduced herein as FIGS. 1 and 2, and illustrate acentrifugal-type implantable blood pump including a housing 14, definingthe flow path for blood passing through the device. This device alsoincludes a stator 56 having a metal wire coil or winding 57. A commonmetal used in such stators is copper wire. Around the stator is a secondhousing 12 which forms a seal around the stator and, once the pump isimplanted into a patient in need thereof, prevents surrounding bodyfluids from contacting the stator.

While current implantable blood pumps provide numerous benefits topatients in need thereof, improvement can be made to the current devicesto provide additional benefits to patients, in addition to potentiallymaking such devices available to an even wider range of patients in needthereof.

BRIEF SUMMARY OF THE INVENTION

In one embodiment of the present invention, an implantable blood pumpincludes a housing defining a flow path, a rotor positioned within theflow path, and a motor including a stator, positioned outside of saidhousing, the stator including a length of silver wire, wherein thesilver wire is not positioned within a hermetically sealed compartmentonce the blood pump is ready for implantation into a patient in needthereof.

The stator of this blood pump may be open to direct contact with bodyfluids. The blood pump of this embodiment may be a centrifugal-typeradial flow blood pump, a radial-flow type blood pump, or the like.Further, the silver wire may be substantially surrounded by aninsulation covering.

The present invention may also include, in another embodiment, a methodof implanting the implantable blood pump including the step ofimplanting the blood pump within the patient and within or adjacent tothe vasculature. Further, upon implanting the blood pump, the silverwire contacts a body fluid. The blood pump may be implanted within theheart, through the wall of the heart, adjacent to the heart, or thelike.

In another embodiment, the present invention may include an implantableblood pump including a housing, a rotor mounted for rotation within saidhousing; a motor including an at least one stator disposed on theoutside of said housing and mounted on said housing; said statorincluding a silver wire coil, wherein the stator is not positionedwithin a hermetically sealed compartment once the blood pump is readyfor implantation into a patient in need thereof.

Further, the at least one stator may include two stators. Moreover, theat least one stator may include three or more stators.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 illustrate an implantable blood pump as known in the priorart.

FIG. 3 illustrates one embodiment of the implantable blood pump of thepresent invention.

FIG. 4 illustrates another embodiment of the implantable blood pump ofthe present invention.

DETAILED DESCRIPTION

The term “implantable blood pumps” as used throughout, is intended torefer generally to blood pumps which may be used within the vasculature,such as within the heart, through the wall of the heart, the aorta, thevarious arteries or veins, or the like, or adjacent to the vasculature,such as adjacent to the wall of the heart or within the abdomen adjacentto the heart or other vasculature. Typically, such blood pumps areimplanted into the left or right ventricle of the heart. One suchexample of an implantable blood pump may be a ventricular assist device(VAD) or other pump which is implantable into a patient in need thereof.

As illustrated in FIG. 3, in one embodiment, an implantable blood pump10, illustrated as a centrifugal-type radial flow blood pump, includes amotor including a stator 56 having a length of metal wire 57 wound intoa coil. The device 10 also includes housing 14 defining a flow path 62therethrough. A rotor 17 (best seen in FIG. 1) is positioned withinhousing 14.

Contrary to the prior art blood pump of FIGS. 1 and 2, however, thedevice of the present invention does not include the housing 12. Housing12 of FIGS. 1 and 2 would, once ready for implantation, create a sealwhich prevented intrusion of outside elements, such as body fluids, fromentering the volume within housing 12 such that the stator, includingthe wire coils, would not come into contact with the body fluids. Such ahousing 12 was necessary to prevent contact between the copper wire ofthe stator and the body fluids surrounding the implanted blood pumpduring the entire lifetime of the pump. A seal which prevents bodyfluids from entering the housing 12 and contacting the stator throughoutthe life of the blood pump is referred to herein as a hermetic seal.

Blood pump 10 in the embodiment of FIG. 3 includes metal wire 57comprised of silver wire. The use of silver wire may eliminate the needfor a secondary housing (such as housing 12) and as such, the need for asealed compartment around the stator. In effect, the use of silver wirein stator 56 allows for contact between the stator and surrounding bodyfluids, upon implantation of the blood pump 10 into the patient in needthereof, to occur. Therefore, a seal, such as a hermetic seal forexample, is not present in pump 10, once the pump 10 is ready forimplantation, and is further not required in the embodiment of FIG. 3.

The silver wire 57 of stator 56 of this embodiment may be a length ofsilver wire, preferably a continuous length of silver wire, wound into acoil around a pole piece (not shown) or other material as known in theart. In this embodiment, the silver wire is a conventional wire, i.e., adiscrete filament of silver. The silver wire 57 may also include aninsulation covering to maintain separation of adjacent portions of thelength of wire upon formation of the coil which may maintain properelectrical flow through the length of the wire. However, such insulationcovering is not intended to prevent contact between the silver wire ofthe stator and the body fluids surrounding the implanted blood pump, andspecifically such insulation covering is not intended to prevent contactbetween the silver wire of the stator and body fluids throughout thelife of the pump 10.

Such silver wire 57, rather than a discrete filament, may also have astructure similar to, for example, a conductor on a circuit board. Inone example, such a structure may be similar to a printed circuit boardin that a silver length of material may form a conductive pathway alonga non-conductive substrate. The silver conductive pathway may belaminated onto the non-conductive substrate in a coil pattern, or thelike, and positioned within the pump 10 as a stator 56. Thus, as used inthis disclosure, the term “wire” includes a conductor disposed on adielectric substrate.

FIG. 3 illustrates a single stator 56 positioned on housing 14. However,pump 10 may have more than one stator, and thus may have two stators,three stators, or more than three stators. In the embodiment of pump 10having three stators 56, such stators would be positionedcircumferentially around housing 14, and mounted on the outside surfaceof housing 14, and a central portion of each stator preferably would bepositioned substantially equidistant from one another (e.g., about 120degrees from one another relative to a central longitudinal axis of pump10). Depending on the size of each stator, a portion of each stator mayoverlap a portion of either or both adjacent stators.

While FIG. 3 illustrates a centrifugal-type implantable blood pump 10,silver wire coils may be used in stators in other types of blood pumps,including axial-flow type blood pumps, such as the pump disclosed inU.S. application Ser. No. 13/163,253, published as U.S. Publication No.2011/0311383, the entirety of which is incorporated by reference hereinas if fully set forth herein. FIG. 4 illustrates such an implantableblood pump 110. In this embodiment, the pump 110 includes a rotor 120positioned within a housing 150 having a flow path 162, a motorincluding an at least one stator 156 disposed on the outside of housing150 and mounted on housing 150, and the stator 156 includes anelectrically conductive length of silver wire 157 coiled around a polepiece or like substrate (not shown). The pump 110 includes at least onestator 156, or, as illustrated, the pump 110 may include two statorssubstantially equidistant from one another—one on one side of thehousing and another on an opposite side of the housing (e.g., about 180degrees from one another relative to a central longitudinal axis of pump110). Depending on the size of each stator, a portion of each stator mayoverlap a portion of either or both adjacent stators. Such equidistantpositioning of the stators may allow for more efficient and smootheroperation of the rotor.

In an alternative arrangement, pump 110 may include at least threestators positioned circumferentially around the housing substantiallyequidistant from one another (e.g., about 120 degrees from one anotherrelative to a central longitudinal axis of pump 110). Depending on thesize of each stator, a portion of each stator may overlap a portion ofeither or both adjacent stators.

As above, the stator silver wire coils 157 are positioned outside of thehousing 150 and thus are not within a sealed volume (e.g., within asecond, outer housing) and are therefore open to direct contact withbody fluids upon implantation of device 110 into a patient in needthereof. Also, as above, the silver wire 157 of this embodiment mayoptionally include an insulation covering to maintain separation ofadjacent portions of the length of wire upon formation of the coil whichmay maintain proper electrical flow through the length of the wire.However, such insulation covering is not intended to prevent contactbetween the silver wire of the stator and the body fluids surroundingthe implanted blood pump, and specifically such insulation covering isnot intended to prevent contact between the silver wire of the statorand body fluids throughout the life of the pump 10.

In another embodiment, the present invention may include a method ofimplanting the implantable blood pump 10, 110 including accessing theinterior of a patient in need thereof and implanting the blood pump 10,110 within the patient in communication with the vasculature. The bloodpump 10, 110 may be implanted within the vasculature, such as within theheart, through the wall of the heart, within the aorta, within thevarious arteries or veins, or the like; or adjacent to the vasculature,such as adjacent to the wall of the heart or within the abdomen adjacentto the heart or other vasculature. Once implanted, the silver wire ofthe stator may come into contact with body fluids. In arrangements ofthis method where the blood pump itself is not implanted within thevasculature, the method may include the further step of implanting aconduit from the pump to the vasculature to create a flow path for theblood to pass between the pump and the vasculature. Typically, bloodpump 110 (FIG. 4) is implanted within the vasculature, while blood pump10 (FIG. 3) is commonly implanted either through the wall of the heartor adjacent to the vasculature.

Numerous benefits may be realized with the use of silver wire in thestator. For example, the use of silver wire may eliminate the need for aseal, for example a hermetic seal, to be placed around the stator. Sincesilver is a biocompatible metal, the contact between bodily fluids andthe silver wire is acceptable. Moreover, it is known that silver doesnot provide for a suitable substrate on which bacteria and otherorganisms can grow, thus leaving the silver wire open to body fluidsshould not provide any increased risk for infection of the surroundinganatomy or rejection of the device 10, 110 by the patient.

The elimination of the outer housing (and thus seal around the stator)may thus result in a device having smaller dimensions and a lighterweight than currently available implantable blood pumps. Such smallerand lighter pumps may be less invasive to the surrounding anatomy andthus make such pumps available to a greater number of patients,particularly, for example, those whose anatomy may not have the strengthor capacity to support a larger blood pump.

Another potential benefit of the use of silver wire in the stator mayrelate to the conductivity of silver. Silver is a better conductor thanother metals currently being used, such as copper (6.3×10⁷ siemens/metervs. 5.96×10⁷ siemens/meter (copper)). Thus, the use of silver ratherthan other metals may decrease the build-up of heat in the implantedpump due to its high conductivity and, inversely, its low resitivity.

Additionally, the increased conductivity and decreased resistance ofsilver may increase battery life. As most implantable blood pumpsoperate using a rechargeable battery pack, a patient using device 10,110 may benefit from a longer length of time between charges of thebattery pack, which may result in an increase in the patient's standardof living and independence.

Although the invention herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent invention. It is therefore to be understood that numerousmodifications may be made to the illustrative embodiments and that otherarrangements may be devised without departing from the spirit and scopeof the present invention as defined by the appended claims.

The invention claimed is:
 1. An implantable blood pump comprising: ahousing defining a blood flow path and a longitudinal axis extendingalong the blood flow path; a rotor positioned within the blood flowpath; and a motor including at least two stators positioned outside ofthe housing and each including a portion overlapping an adjacent statorand a silver wire forming a distalmost outer region of a portion of ablood pump relative to the longitudinal axis, the silver wire beingconfigured to directly contact a body fluid when implanted within apatient.
 2. The blood pump of claim 1, wherein the blood pump is acentrifugal-type radial flow blood pump.
 3. The blood pump of claim 1,wherein the blood pump is an axial-flow type blood pump.
 4. The bloodpump of claim 1, wherein the silver wire is positioned as a coil on theoutside of the housing and the silver wire is substantially surroundedby an insulation covering adapted to maintain separation of adjacentportions of the coil to maintain proper electrical flow and does notprevent contact of the silver wire with the body fluid.
 5. The bloodpump of claim 1, wherein the silver wire is a conductor pathwaylaminated onto a dielectric substrate.
 6. A method of implanting animplantable blood pump, the method comprising: providing an implantableblood pump including: a housing defining a blood flow path and alongitudinal axis extending along the blood flow path; a rotorpositioned within the blood flow path; and a motor including at leasttwo stators positioned outside of the housing and each including aportion overlapping an adjacent stator and a silver wire forming adistalmost outer region of a portion of a blood pump relative to thelongitudinal axis; and implanting the implantable blood pump into one ofa heart and through a wall of the heart of a patient.
 7. The method ofclaim 6, wherein upon implanting the implantable blood pump, the silverwire contacts a body fluid.
 8. An implantable blood pump, comprising: ablood pump housing defining a blood flow path and a longitudinal axisextending along the blood flow path; a rotor mounted for rotation withinthe blood pump housing; and a motor including at least two statorsmounted on an outside of the blood pump housing, the at least twostators each including a portion overlapping an adjacent stator and asilver wire coil forming a distalmost outer region of a portion of ablood pump relative to the longitudinal axis.
 9. The blood pump of claim8, wherein the pump is a centrifugal-type radial flow blood pump. 10.The blood pump of claim 8, wherein the pump is an axial-flow type bloodpump.
 11. The blood pump of claim 8, wherein the at least two statorsincludes at least three stators.
 12. The blood pump of claim 8, whereinthe silver wire coil is substantially surrounded by an insulating sheathadapted to maintain separation of adjacent portions of the coil tomaintain proper electrical flow and permit contact of the silver wirewith a body fluid.
 13. The blood pump of claim 8, wherein the silverwire coil is a conductor pathway laminated onto a dielectric substrate.